Hydroforming process with molybdena on alumina-silica catalyst



United States Patent Otto Schricker, In, Nixon,

and Engineering Company,

No Drawing. Application November 10, 1953 Serial No. 391,385

6 Claims. (Cl. 208-136) NJ., assignor to Esso Research a corporation of Delaware This invention relates to improvements in the hydroforming of hydrocarbons. More particularly it relates to improvements in hydroforming wherein a molybdena catalyst on a carrier containing a major proportion of aluminum and a minor proportion of silica is activated at elevated temperatures and utilized while still hot in the hydroforming reaction.

Hydroforming is defined as an operation in which a petroleum naphtha is contacted at elevated temperatures and pressures and in the presence of a recycled hydrogencontaining gas with a solid catalytic material under conditions such that there is no net consumption of hydrogen. Usually the feed stock boils substantially within the range of from about 150-430 F. and more particularly 200-350 F. The light ends, i.e., the material boiling from about 2-00 F., are not usually subjected to this reaction, for the reason that the virgin naphtha light endshave a fairly good octane rating. The feed or charging stock to the hydroforming reactior can be a virgin naphtha, a cracked naphtha, a Fischer- Tropsch naphtha, a mixture of these, or the like.

Hydroforming operations are ordinarily carried out in the presence of hydrogen or hydrogen-rich recycle gas at temperatures of 7501150 F., in a pressure range of about 50 to 1000 pounds per square inch, and in con- .tact with such molybdena type catalysts as molybdenum oxide, chromium oxide, or, in general, oxides or sulfides of metals of groups IV, V, VI, VII, and VIII of the periodic system'of elements alone, or generally supported on a base or spacing agent such as alumina gel, precipitated alumina, or zinc aluminate spinel. A good hydroforming catalyst is one containing about '10 weight percent molybdenum oxide upon an aluminum oxide base prepared by heat treating a hydrated aluminum oxide or upon a Zinc aluminate spinel.

The chemical reactions involved in the hydroforming process include dehydrogenation of naphthenes to the corresponding aromatics, isomerization of straight chain paraflins to form branched chain paraflins, isomerization of cyclic compounds such as ethylcyclopentane to form methylcyclohexane, and some aromatization, dealkylation and hydrocracking of paraflins. In a hydroforming operation which is conducted efiiciently it is possible with the use of a proper catalyst and proper conditions of operation to hydroform a virgin naphtha having an octane number of about 50 to a hydroformate having an octane number of from 95 to 98 and obtain yields of C hydrocarbons as high as 85%.

It has been proposed in application Serial No. \188, 236, filed October 3, 1950, now U. S. Patent No. 2,689,823, to effect the hydroforming of naphtha fractions in the presence of a dense fluidized catalyst mass in a fluidized solids reactor system in which naphtha vapors are passed continuously through the dense, fluidized bed of hydroforming catalyst particles in a reaction zone, spent cataice lyst particles being withdrawn from the dense bed in the reaction zone and passed to a separate regeneration zone where fouling, deactivating carbonaceous deposits are removed by combustion, whereupon the regenerated catalyst particles are returned to the main reactor vessel. Fluid hydroforming, as thus conducted, has several fundamental advantages over fixed bed hydroforming such as (1) the operations are continuous, v(Z) the vessels and equipment can be designed for single rather than dual functions, (3) the reactor temperature is substantially constant throughout the bed, and (4) the regeneration or reconditioning of the catalyst may be readily controlled.

A particularly useful catalyst for these operations has been found to be molybdic oxide supported on an active alumina-containing base. The molybdic oxide utilized in the catalyst based on the base is in the range of 5 to 15 weight percent, usually about 10 weight percent. This catalyst has also been found useful in a variety of other hydrocarbon conversion reactions such as hydrogen transfer.

In a prior application filed in the name of Charles E. Hemminger on October 31, 1952, Serial No. 318,000, now abandoned, for Improvements in Hydroforming, there is described and claimed a method of preparing an improved attrition resistant catalyst base containing a major proportion af aluminum and a minor proportion of silica prepared by mixing together aluminum sulfate, sodium aluminate and a relatively small amount of sodium silicate in an aqueous medium maintained at a final pH of between 9 and 10. The slurry resulting from this mixture is filtered and washed several times and finally spray-dried. This base contains from 1 to 5 weight percent, and preferably about 2 weight percent, silica.

In preparing the hydroforming catalyst itself by the preferred impregnation method, the base or carrier is impregnated with a water-soluble molybdenum salt which is, at the same time, heat decomposable,.e.g., ammonium molybdate. The impregnated base is dried, heated and calcined. The amount of molybdenum salt impregnated into the base is such as to give a molybdenum oxide (M00 content of about 10% based on the total weight of the catalyst.

The catalyst can also be prepared by the so-called dry mix method. In that process the base is simply mixed with molybdic oxide. The catalyst thus can be prepared by a simple mixing of the dry powders and pelleting. The catalyst is then activated by heating in air or nitrogen at a temperature of about 1200 F. some time prior to use.

Because of the large quantities of feed stocks that are processed in reactions such as hydroforming, a good deal of research has been expended in improving the selectivity and activity of the conversion in the use of the molybdic oxide-alumina silica catalysts. The selectivity is defined as the gasoline yield for a given octane number product.

It has now been found that the activity of these particular molybdena catalysts, i.e., wit-h carriers containing a major proportion of alumina and a minor proportion of silica, is appreciably improved by beating them to a temperature of 1400-1500 F. for from one to six hours in a flowing stream of inert gas and charging the catalyst to thehydroforming process while the catalyst is still hot, i.e., so that it has not cooled down below a minimum temperature of 750 F. immediately prior to its use in the process.

The process of this invention is thus applicable to a fixed bed or fluidized process, although the latter is pre- Conditions in reactor ferred and is particularly suited for fresh makeup catalyst. The catalyst is calcined, preferably in a fluid bed itself, Preferred Range in a calciner utilizing an inert gas. In fixed bed hydroformers a direct fired rotary kiln could be used to calcine 5 Catalyst Composition 10% M; 545% M00; catalyst while a reactor was being charged. The heat ,f ff f j 83 8 81 1538 treatment of this invention is utilized even though the Catalyst'to oil ratio 0. 5-3.0 0.1 to7 catalyst system has originally been calcined during the gggg lf sf igl ggl gg asoo-g egg 2,000-10,00g course of its preparation.

The temperature utilized is important. Temperatures 10 below 1400 F. give inferior results, whereas high tem- Conditions in regenerate, peratures give excessive loss of molybdena. The deleterious elfects of higher temperatures can be avoided f d Ran e somewhat by feeding in vaporized molybdena with the m me E fluidizing gas in a fluidized heat treatment. The heat- Temperature'q, MOHYQOO M11250 mg of the fluidized gas itself can be accomplished by 11;re53ure,p5.i.g t. 150 223 53328 bringing the gas to the desired temperature by convenesi 90 ime, 95 tional means in a direct fired furnace. It can also be Flumlzmg gasvelomy heat exchanged with the reactor effluent and then with regenerator flue gas. The remaining heat to raise the In the fluid hydroforming process itself the feed stock temperature would then be supplied by a furnace. is preheated alone or in admixture with recycle gas to The inert gases that can be utilized in the heat treatreaction temperature or to the maximum temperature posment include air, nitrogen, and recycle gas containing sible while avoiding thermal degradation of the feed water up to about 5 mole percent, scrubbed to remove stock. Ordinarily preheating of the feed stock is carried all carbon and sulfur compounds, and regenerator flue out to temperatures of about 800 -1000 F., preferably gas, with all carbon and sulfur compounds removed, givabout 950 F. The naphtha preheat should be as high ing a gas high in N and already at an elevated temas possible while avoiding thermal degradation thereof perature. It is important that the gas be flowing rather as by limiting the time of residence in the transfer or than stagnant, as data show that stagnant gases give far feed inlet lines. The preheated feed stock may be supinferior results. Flow rates as low as 10 v./hr./v. can plied to the reaction vessel in admixture with hydrogem be used, but it is preferable to employ 1000-4000 v. of rich recycle gas or it may be introduced separately. The gas/hr./v. catalyst. recycle gas, which contains from about 50 to 85 volume It is also important that the catalyst be utilized impercent hydrogen, is preheated to temperatures of about mediately after being subjected to the heat treatment or ll50-1200 F., preferably about 1185 F., prior to the as close thereto as possible. The minimum temperature introduction thereof into the inlet line. The recycle gas to which it can be cooled controls this feature. should be circulated through the reactor at a rate of from This invention will be better understood by reference about 1000 to 8000 cubic feet per barrel of naphtha feed. to the following examples showing the effect on the ac- The amount of recycle gas added is preferably the minitivity of a catalyst processed as taught in this invention mum amount that will suflice to carry the necessary heat and the conditions of operation of various components 40 of reaction into the reaction zone and keep the carbon utilized in a fluidized process. formation at asatisfactory low level The reactor system is charged with a mass of finely EXAMPLE I divided hydroforming catalyst particles. The catalyst Catalysts containing 10% y na onNalco HF-85 particles are, for the most part between 200 and 400 alumina containing Weight Percent Silica 011 5 mesh in size, or about O200 microns in diameter, with the base) were utilized in a hydroforming process. The a major proportion between 20 and 80 microns. molybdena had been P On the Carrier y impregnation, Space velocity or the weight in pounds of feed charged the preferred method. The catalysts, except the control, per hour per pound of catalyst in the reactor depends were all heated to 1400" F. under varying conditions as upon the age or activity level of the catalyst, the charset forth in the table below. They were then utilized acter of the feed stock, and the desired octane number in controlled Y g Operations at 9 200 of the product. Space velocity may vary, for example, p.s.i.g., 5000 s.c.f./b. of once-through hydrogen, and from about 1.5 wt./hr./wt. to about 0.15 wt./hr./wt. 0.7 mole percent H O, utilizing a virgin naphtha boil- It is to be understood that this invention is not limited ing in the range of 200 330 F. to the specific examples, which have been offered merely Control 1 2 3 4 CalclnatlonTemp.,F 1,200 1,400 1,400 1,400 1,400. Calcinntion Time, Hours 6 6. CalclnedinPi-esence of Stagnant Flowing Flowing Flowing stagnant Air. N1. N1. N1. Air. Time of Storage Prior to Use-Days.... 270 3 30 0. Activity-WJHn/ll'.for 95 0.N 0.35 0.80 0.53 0.33 0.2.

These figures demonstrate how the maximum activity was as illustrations, and that modifications may be made withobtained with a catalyst used immediately after being out departing from the spirit of the invention. heated and that the activity declined sharply with the What is claimed is: storage time of the catalyst. The flowing gas was also 1. In a process for hydroforming petroleum naphthas shown to be important. The improvement over the conin contact with finely divided molybdena catalyst partrol is apparent. Other data show that the activity obticles at 750 to 1150 F., said molybdena being on a tained by heating to 1400-1500 F. is superior to that carrier containing a major proportion of alumina and a gotten from heating at lower temperature. There is no minor proportion of silica, and inaccordance with the difference on the utilization of different inert gases as fluidized solids technique, the improvement which comlong as the desired flowing features prevail. prises heating the catalyst to a temperature of 1400'- The following conditions are those utilized in a typical 1500 F. for from one to six hours in a flowing stream fluidized process.

of inert gas cooling the heated catalyst to a temperature of above 150 F., and charging said hot catalyst to the hydroforming process immediately so that it does not cool down below a minimum temperature of 750 F.

2. The process of claim 1 in which the molybdena catalyst is prepared by impregnation on the carrier.

3. The process of claim 1 in which the catalyst contains from about 5 to 15 Weight percent molybdena and th carrier contains from about 1 to 5 weight percent silica.

4. The process of claim 1 in which the molybdena catalyst is prepared by admixing with the carrier.

5. In a process for the hydroforming of petroleum naphthas at elevated temperatures in the range of 750 to 1150 F. and pressures utilizing a molybdic oxide catalyst supported on an active alumina-containing base, the improvement which comprises heating the catalyst to a temperature of 1400l500 F. for from 1 to 6 hours in a flowing stream of inert gas, cooling the heated catalyst to a temperature of above 750 F. and charging said hot catalyst to the hydroforming process immediately so that it does not cool down below a minimum temperature of 75 0 F.

6. The process according to claim 5 in which said hydroforming process takes place at a temperature of from 750 to 950 F., said catalyst contains from about 5-15% molybdic oxide, and said carrier contains from about 1-5 wt. percent silica.

References Cited in the file of this patent UNITED STATES PATENTS 2,426,118 Parker et al Aug. 19, 1947 2,432,822 Secor Dec. 16, 1947 2,437,531 Hufiman Mar. 9, 1948 2,487,564 Layng Nov. 8, 1949 2,608,534 Fleck Aug. 26, 1952 2,676,907 Oblad et al Apr. 27, 1954 2,768,933 Burton et a1 Oct. 30, 1956 

1. IN A PROCESS FOR HYDROFORMING PETROLEUM NAPHTHAS IN CONTACT WITH FINELY DIVIDED MOLYBDENA CATALYST PARTICLES AT 750 TO 1150* F., SAID MOLYBDENA BEING ON A CARRIER CONTAINING A MAJOR PROPORTION OF ALUMINA AND A MINOR PROPORTION OF SILICA, AND IN ACCORDANCE WITH THE FLUIDIZED SOLIDS TECHNIQUE THE IMPROVEMENT WHICH COMPRISES HEATING THE CATALYST TO A TEMPERATURE OF 1400*1500* F. FOR FROM ONE TO SIX HOURS IN A FLOWING STREAM OF INERT GAS COOLING THE HEATING CATALYST TO A TEMPERATURE OF ABOVE 150*F., AND CHARGING SAID HOT CATALYST TO THE HYDROFORMING PROCESS IMMEDIATELY SO THAT IT DOES NOT COOL DOWN BELOW A MINIMUM TEMPERATURE OF 750*F. 